Primates make extensive use of binocular, frontal vision in their daily behavior. Much of our visual function is dedicated to central (foveal) vision where retinal ganglion cell densities and the associated cortical magnification factor are highest. To examine an object in detail its image must be kept relatively stable on or near the fovea. This is accomplished by foveating (e.g., smooth pursuit and saccades) and stabilizing (e.g., optokinetic and vestibular ocular) eye movement systems. The visual and oculomotor systems of human and non-human primates are immature at birth and sensitive to injury. At least 3% of children born in the United States have compromised visual and eye movement function leading to misalignment of the eyes (strabismus), impaired gaze-holding (nystagmus), disorders of eye movements (smooth pursuit asymmetry, dysconjugacy) and amblyopia. The long-term goal of this project is to determine neural mechanisms that could be causal for these disorders. Our overarching hypothesis is that specific regions of the frontal and parietal cortex and their brainstem targets contribute differentially to defective eye movements, gaze-holding, eye misalignment, and impaired visual function. To address these problems, we have developed macaque models for infantile strabismus, which have virtually the same syndrome components as those observed in children with developmental strabismus. We use single unit recording during smooth pursuit and other tracking behaviors to determine how neural circuits are altered in developmental strabismus. The significance of our work is that different developmental or disease processes lead to permanent loss of visual-oculomotor function across the lifespan. Yet we know relatively little about how neural circuits are compromised in developmental disorders like strabismus and amblyopia. Therefore, our studies are designed to test real neural circuits in a manner that will aid in the diagnosis, treatment and cure of disorders associated with strabismus, neurodegenerative disease and brain injury.